信息不对称、过度自信与股价变动

信息传导的非同步和投资者情绪变化是股票市场的两个典型特征,前者会引发投资者之间出现信息不对称问题,后者主要体现为投资者过度自信,两者共同作用影响股票价格变动。本文将信息不对称和投资者过度自信情绪置于同一个分析框架,建立两阶段动态序贯定价理论模型研究现实市场上信息传导过程中股价变动的内在机制。结果表明:(1)面临新信息的进入,投资者对股票收益预期的调整与均衡价格之间具有正相关关系;(2)面临有利消息时,过度自信投资者比例越大,股票的均衡价格越高,投资收益将越低;面临不利消息时则相反;(3)随着过度自信投资者比例以及过度自信程度升高,市场风险溢价将下降;(4)投资者群体在信息传导过程中出现分化,对股价变动形成异质信念,未获取信息和获取信息但未出现过度自信的投资者认为股价被高估,获取信息且出现过度自信的投资者认为价格被低估,促使更多的交易,引发市场成交量和股价变动;(5)过度自信投资者比例与过度自信程度提高均会对市场效率产生正向影响,而对市场深度具有负向效应。最后,基于理论结果对非对称性和持续性等典型的市场波动性特征进行解释。     

Do investors care about credit ratings? An analysis through the cycle

We investigate how the credit cycle affects the link between bond spreads and credit ratings. Using a simple model of the credit assessment process, we show that when the debt market is more opaque, the information content of ratings deteriorates, creating an incentive for investors to increase the amount spent on private information. We test this hypothesis empirically. Results show that when market opaqueness (proxied by the spread between Aaa- and Baa-rated bonds) increases, the explanatory power of ratings and other control variables deteriorates as investors increasingly price in non-public information.     

基于异质信号的资产价格学习机制及均衡演化路径

本文从金融市场指令交易机制出发,将市场投资主体分为市场追随者和自我相信者两类,分析了两类投资者面对由异质分析资产价值信号形成的市场价格的学习机制,且对交易量变化以及均衡价格的达成路径进行了研究。研究表明,单期价格均衡下市场仍存在资产交易,且投资者随着均衡价格期数增加和价格精度增大逐渐撤离市场,较大的市场追随者比重将滞后混合策略市场的价格均衡期数。     

How do individual investors trade?

This paper examines how high-frequency trading decisions of individual investors are influenced by past price changes. Specifically, we address the question as to whether decisions to open or close a position are different when investors already hold a position compared with when they do not. Based on a unique data set from an electronic foreign exchange trading platform, OANDA FXTrade, we find that investors’ future order flow is (significantly) driven by past price movements and that these predictive patterns last up to several hours. This observation clearly shows that for high-frequency trading, investors rely on previous price movements in making future investment decisions. We provide clear evidence that market and limit orders flows are much more predictable if those orders are submitted to close an existing position than if they are used to open one. We interpret this finding as evidence for the existence of a monitoring effect, which has implications for theoretical market microstructure models and behavioral finance phenomena, such as the endowment effect.     

Price Formation and Liquidity in the U.S. Treasury Market: The Response to Public Information

The arrival of public information in the U.S. Treasury market sets off a two-stage adjustment process for prices, trading volume, and bid-ask spreads. In a brief first stage, the release of a major macroeconomic announcement induces a sharp and nearly instantaneous price change with a reduction in trading volume, demonstrating that price reactions to public information do not require trading. The spread widens dramatically at announcement, evidently driven by inventory control concerns. In a prolonged second stage, trading volume surges, price volatility persists, and spreads remain moderately wide as investors trade to reconcile residual differences in their private views.     

News release and the role of different types of investors

We examine how investors react to positive and negative news in the Chinese stock market. We show that positive news is followed by a reversal in stock price, while negative news reports are accompanied by a drift. Using a unique account-level dataset, we find that institutional investors' attention bias contributes to the market's absorption process for different types of news, which is different from the conclusion that the phenomenon is driven by retail investors in the U.S. market. We explain the differences between the two markets as the short-sale constraints induce the attention bias of institutional investors in China. Individual investors are not able to correctly judge the content of news reports, and act as a liquidity provider. We highlight the market regulation plays an important role in the process of investors analyzing information.     

Coexistence of disposition investors and momentum traders in stock markets: experimental evidence

Prior research documents that many investors disproportionately hold on to losing stocks while selling stocks which have gained in value. This systematic behavior is labeled as the “disposition effect”. The phenomenon can be explained by prospect theory's idea that subjects value gains and losses relative to a reference point like the purchase price (PP), and that they are risk-seeking in the domain of possible losses and risk-averse when a certain gain is obtainable. Our experiments were designed to test whether individual-level disposition effects attenuate or survive in a dynamic market setting. We analyze a series of 36 stock markets with 490 subjects. The majority of our investors demonstrate a strong preference for realizing winners (paper gains) rather than losers (paper losses). We adopt different reference points and compare the behavioral patterns across three main trading mechanisms, i.e. rules of price formation. The disposition effect is greatly reduced only within high-pressure mechanisms like a dealer market (DM) when the last price (LP) is assumed as a reference point, which is a more market driven (external) benchmark. If disposition investors use the PP as a reference point, which is a more mental-accounting driven (internal) benchmark, they die hard in all market settings. Interestingly, our markets do not collapse or become illiquid by disposition investors' reluctance to trade. A main reason for this is the coexistence of two or more groups of investors, e.g. momentum traders and disposition investors.     

The market for credit default swaps: new insights into investors' use of accounting information?

The market for credit default swaps has developed into a well‐functioning, global multi‐trillion dollar market, wherein investors price and transfer corporate financial instruments on the basis of credit risk. This paper first summarizes the structure and growth of the market. Next, I introduce theory and evidence on how investors price credits risk and explain how the quality of financial statement information plays a unique role in the determination of credit spread. I then review the nascent empirical accounting literature on this topic. This review sheds light on several accounting research questions that might be understood better in the setting of the credit default swap market. The final section summarizes suggestions for future work.     

Determinants of bid and ask quotes and implications for the cost of trading

Financial transaction costs are time varying. This paper proposes a model that relates transaction cost to characteristics of order flow. We obtain qualitatively consistent model results for different stocks and across different time periods. We find that an unusual excess of buyers (sellers) relative to sellers (buyers) tends to increase the ask (bid) price. Hence, the ask and bid components of spread change asymmetrically about the efficient price. For a fixed order imbalance surprise these effects are muted when unanticipated total volume is high. Unexpected high volatility in the transaction price process tends to widen the spread symmetrically about the efficient price. Our findings are consistent with predications from market microstructure theory that the cost of market making should depend on both the risk of trading with better-informed traders and inventory risk. We also find that order flow surprises have a significant impact on the efficient price and can also explain a substantial amount of persistence in the volatility of the efficient price. This dependence does not violate the efficient market hypothesis since the surprises, by definition, are not predictable.     

Bayesian Investor Belief Updating Speed and Market Underreaction to Earnings Announcements

Building on the Bayesian Theorem, we propose a multi-period market microstructure model to understand how Bayesian investors underact new information and the duration of market underreaction. Applying the model to post-earnings-announcement drifts, our simulation and regression analyses show that the duration of the post-announcement price adjustment process and the post-announcement drifts can be explained by the new measure of belief updating speed that quantifies the uncertainties faced by Bayesian investors when incorporating new information into prices. Our study highlights the importance of incorporating the belief uncertainties of uninformed investors in explaining market underreaction in the Bayesian framework.     

STOCK MARKET OPENNESS AND MARKET QUALITY: EVIDENCE FROM THE SHANGHAI–HONG KONG STOCK CONNECT PROGRAM

We study the impact of capital market openness on high-frequency market quality in China. The Shanghai–Hong Kong Stock Connect program (SHHKConnect) opens China's stock market to foreign investors and offers a natural experiment to investigate this question. Using a difference-in-differences approach, we find that market liberalization leads to lower quoted spread, lower effective spread, lower market depth, and higher short-term volatility. Our findings imply that opening the markets to more sophisticated foreign investors is associated with higher competition and more cross-market arbitrage activities, narrowing the spread and reducing liquidity providers’ profits, but increasing the price impact and short-term volatility of connected stocks.     

Stock price synchronicities and speculative trading in emerging markets

The literature suggests that the strong price synchronicity observed in emerging markets is driven by the lack of firm-specific information acquisition. This paper extends previous studies by focusing on the question of whether investors’ speculative trading behavior or market conditions make the synchronicity in emerging markets more pronounced. Our results indicate that the propensity to engage in speculative trades and a low level of linkage with the world market lead to greater stock price synchronicity. These results are consistent with the hypotheses that it is difficult to price firm-level fundamentals in a speculative market where noise trades prevail, and that less weight is attached to firm-specific fundamentals in pricing stocks in a more segmented market. The price synchronicities are largely found to be stronger in bearish markets, a finding consistent with the hypothesis that investors have increased loss aversion during bear markets, which further limits informed arbitrage.     

An Equilibrium Model of Asset Trading with Sequential Information Arrival

In an effort to better understand the dynamic market price adjustment process, this paper develops a model which describes the impact of new information on a financial market. The primary emphasis is on the price change-volume relationship in the presence of a margin requirement. We find that the margin requirement significantly affects the relation of price change to volume. Furthermore, this relationship is shown to be affected by the number of investors in the market, the degree of information dissemination, differences in interpretation of information and the implicit cost of the margin requirement.     

Effects of Price Regulations and Dark Pools on Financial Market Stability: An Investigation by Multiagent Simulations

We built an artificial market model and investigated the impact of large erroneous orders on financial market price formations. Comparing the case of consented large erroneous orders in the short term with that of continuous small erroneous orders in the long term, if amounts of orders are the same, we found that the orders induced almost the same price fall range. We also analysed effects of price variation limits for erroneous orders and found that price variation limits that employ a limitation term shorter than the time erroneous orders exist effectively prevent large price fluctuations. We also investigated effects of up-tick rules, adopting the trigger method that the Japan Financial Services Agency adopted in November 2013. We also investigated whether dark pools that never provide any order books stabilize markets or not using the model including one lit market, which provides all order books to investors, and one dark pool. We found that markets become more stable as the dark pool is increasingly used. We also found that using the dark pool more reduces the market impacts. However, if other investors’ usage rates of dark pools become too large, investors must use the dark pool more than other investors to avoid market impacts. When a tick size of a lit market is larger, dark pools are more useful to avoid market impacts. These results suggest that dark pools stabilize markets when the usage rate is under some threshold and negatively affect the market when the usage rate is over that threshold. Our simulation results suggest the threshold might be much larger than the usage rate in present real financial markets. This study is the first to discuss whether or not several concrete and actually adoptable regulations, including those that have never been employed (e.g. price variation limits with various parameters), could prevent large fluctuations of market prices, including those beyond our experience, using artificial market simulations, and to discuss quantitatively how spreading of dark pools beyond our experience could affect market price formations using the artificial market simulations. In short, this study is the first study to comprehensively discuss how regulations and financial systems beyond our experience could affect price formations using the artificial market simulations. Copyright © 2015 John Wiley & Sons, Ltd.     

Second order approximations for limit order books

In this paper, we derive a second order approximation for an infinite-dimensional limit order book model, in which the dynamics of the incoming order flow is allowed to depend on the current market price as well as on a volume indicator (e.g. the volume standing at the top of the book). We study the fluctuations of the price and volume process relative to their first order approximation given in ODE–PDE form under two different scaling regimes. In the first case, we suppose that price changes are really rare, yielding a constant first order approximation for the price. This leads to a measure-valued SDE driven by an infinite-dimensional Brownian motion in the second order approximation of the volume process. In the second case, we use a slower rescaling rate, which leads to a non-degenerate first order approximation and gives a PDE with random coefficients in the second order approximation for the volume process. Our results can be used to derive confidence intervals for models of optimal portfolio liquidation under market impact.     

投资者异质性与证券市场定价——理论模型与中国的经验证据

本文从投资者异质性的客观现实出发,通过对投资者二维视角的交叉分类与相关行为的探讨,提出了一种按交易特点与行为依据的新的分类方案,即将投资者分为套利交易者、价格预期交易者和量能变动交易者三类。在此基础上分别建立了各类投资者的需求函数,通过对证券市场供求函数的讨论,利用均衡分析方法构建了基于投资者异质性的证券市场定价模型,并以我国证券市场1999-2011年的月度数据为样本进行了实证分析。实证结果表明:我国证券市场价格主要由价格预期交易者的诱导性策略行为与量能变动交易者的羊群行为决定,套利交易者的套利行为对市场价格没有显著的影响,证券市场扩容也未对市场价格的形成产生系统性冲击。     

Market Segmentation and Foreign Share Discount in China

In this paper, I formulate and test a one-period capital asset pricing model under ownership restrictions to explain the price differentials between the classes of shares that can be bought by Chinese citizens and by foreign investors, respectively. I find that time-series variability in the spread between domestic and foreign share returns is consistent with differences in risk exposures and expected risk premium, thus supporting the hypothesis of effective market segmentation and price discrimination. I also find that cross-sectional differences between domestic and foreign share returns are correlated with individual shares'; market betas. The result further supports the price discrimination hypothesis.     

IPO限价发行与新股二级市场价格泡沫——论股票市场“弹簧效应”

本文通过对比2009年7月1日至2014年6月30日IPO市场化定价发行阶段与2014年7月1日至2018年6月30日IPO限价发行阶段共1950个IPO样本,发现IPO限价发行对于新股在二级市场股价表现具有“弹簧效应”:即抑制股票一级市场发行价格会造成新股在二级市场价格短期内超涨,限价发行新股的二级市场定价显著高于市场化定价发行新股的二级市场定价。限价发行引起的过高二级市场定价最终导致股票长期回报率低下。另外,创业板公司“弹簧效应”显著强于主板公司。这些实证结果都可以被本文提出的一级市场价格压抑造成二级市场非理性投资者上涨预期一致、盲目追涨的理论模型所解释。本文的研究指出抑制股票一级市场定价虽然形式上可以解决新股发行价过高问题,但是却造成二级市场更大的价格扭曲。这一发现为进一步完善我国IPO发行定价机制提供了依据。     

Dynamic price discovery

This article analyzes the dynamic process of price discovery in a competitive securities market where investors are equally informed about the fundamental determinants of an asset's end-of-period value but, because they do not know each other's wealth positions, do not know the equilibrium price of shares at the start of a current trading session. Because a large number of participants is assumed, issues concerning market impact and market manipulation are avoided. As trading progresses, participants update their expectations of an asset's equilibrium value. As they do so, price can either converge to a new level or, following a run, revert back to a previous level. This implies that, in clusters of adjacent prices, price changes are more apt to be predominantly of like sign (positive or negative) than would be the case under random walk with a bid-ask spread. Moreover, reversals, when they do occur, should be larger than continuations. An examination of 1988 transactions data for the 30 Dow Jones Industrial stocks shows that this is indeed the case. With the effect of the bid-ask spread removed, first-order autocorrelation coefficients are found to be positive.     

Traders’ choice between limit and market orders: evidence from NYSE stocks

In this paper, we examine a trader's order choice between market and limit orders using a sample of orders submitted through NYSE SuperDot. We find that traders place more limit orders relative to market orders when: (1) the spread is large, (2) the order size is large, and (3) they expect high transitory price volatility. A rise in informational volatility appears neither to increase nor decrease the placement of limit orders. We also find that a rise in lagged price volatility decreases the size of spread, which is driven by the increase in the placement of limit orders.